This Day in History
Jupiter's Io Observed by Spacecraft Galileo (2001)
Photographs taken and transmitted by Galileo, the unmanned spacecraft launched in 1989, allowed scientists to learn more about lo, the innermost of Jupiter's four Galilean moons. The images revealed erupting volcanoes and extraordinary variations in color and brightness. Other data indicated that lo has an iron core and might have its own gravitational field. What is the origin of Io's name?